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Appendix XXI. Fluid dynamic and thermal dynamic experiments<br />

setup for future validation<br />

XXI.1 Validation of dynamic fluctuating airflow velocity and reverse flow in<br />

HADT<br />

The setup for airflow velocity and reverse flow in HADT can be as below:<br />

Figure XXI. 1 The setup for measuring the fluctuating airflow velocity and reverse flow in HADT<br />

The measurement can start after the “breath load” from the lung simulator is adjusted.<br />

The two sections of tube between the chamber and the mask should be the same length<br />

of a single HADT. The NDD Ultrasonic Flow Sensor’s fluctuating reading will be<br />

compared with the model output. When the reading is negative, it means there is reverse<br />

flow. The sum of these negative reading multiplied by the reading interval will be the<br />

experimental result of how far the reverse flow can go. This will be compared with the<br />

output from model.<br />

XXI.2 Validation of CO2 re-breathing<br />

Since CO2 is colourless, transparent and odourless, it is difficult to measure or observe<br />

the re-breath of CO2 or exhaled air. Smoke can be used to measure the re-breath. The<br />

setup is shown in Figure XXI. 2 below.<br />

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